`x-4y+3z-2w=9`
`3x-2y+z-4w=-13`
`-4x+3y-2z+w=-4`
`-2x+y-4z+3w=-10`
The above system of equations can be represented by the coefficient matrix A and right hand side matrix b as follows:
A=`[[1,-4,3,-2],[3,-2,1,-4],[-4,3,-2,1],[-2,1,-4,3]]`
b=`[[9],[-13],[-4],[-10]]`
The augmented matrix can be written as,
`[[A,b]]=[[1,-4,3,-2,9],[3,-2,1,-4,-13],[-4,3,-2,1,-4],[-2,1,-4,3,-10]]`
Now lets, perform the various row operations to bring the above matrix in the row-echelon form,
Rewrite the 2nd Row `(R_2)` as `(R_2-3R_1)`
`[[1,-4,3,-2,9],[0,10,-8,2,-40],[-4,3,-2,1,-4],[-2,1,-4,3,-10]]`
Rewrite the 3rd Row`(R_3)` as`(R_3+4R_1)`
`[[1,-4,3,-2,9],[0,10,-8,2,-40],[0,-13,10,-7,32],[-2,1,-4,3,-10]]`
Rewrite the 4th Row`(R_4)` as`(R_4+2R_1)`
`[[1,-4,3,-2,9],[0,10,-8,2,-40],[0,-13,10,-7,32],[0,-7,2,-1,8]]`
Rewrite the 2nd Row`(R_2)` as`(2(R_2+R_3)-R_4)`
`[[1,-4,3,-2,9],[0,1,2,-9,-24],[0,-13,10,-7,32],[0,-7,2,-1,8]]`
Rewrite the 3rd Row`(R_3)` as`(R_3+13R_2)`
`[[1,-4,3,-2,9],[0,1,2,-9,-24],[0,0,36,-124,-280],[0,-7,2,-1,8]]`
Rewrite the 4th Row`(R_4)` as `(R_4+7R_2)`
`[[1,-4,3,-2,9],[0,1,2,-9,-24],[0,0,36,-124,-280],[0,0,16,-64,-160]]`
Rewrite the 3rd Row`(R_3)` as `(R_3-R_4)`
`[[1,-4,3,-2,9],[0,1,2,-9,-24],[0,0,20,-60,-120],[0,0,16,-64,-160]]`
Rewrite the 3rd Row by dividing it with 20,
`[[1,-4,3,-2,9],[0,1,2,-9,-24],[0,0,1,-3,-6],[0,0,16,-64,-160]]`
Rewrite the 4th Row by dividing it with 16,
`[[1,-4,3,-2,9],[0,1,2,-9,-24],[0,0,1,-3,-6],[0,0,1,-4,-10]]`
Rewrite the 4th Row as `(R_3-R_4)`
`[[1,-4,3,-2,9],[0,1,2,-9,-24],[0,0,1,-3,-6],[0,0,0,1,4]]`
Now the matrix is in row-echelon form, and we can perform the back substitution on the corresponding system,
`x-4y+3z-2w=9` ----- Eq:1
`y+2z-9w=-24` ----- Eq:2
`z-3w=-6` ----- Eq:3
`w=4`
Substitute back the value of w in Eq:3,
`z-3(4)=-6`
`z-12=-6`
`z=-6+12`
`z=6`
Substitute back the value of w and z in Eq:2,
`y+2(6)-9(4)=-24`
`y+12-36=-24`
`y=-24+36-12`
`y=0`
Substitute back the value of w,z and y in Eq:1,
`x-4y+3z-2w=9`
`x-4(0)+3(6)-2(4)=9`
`x+18-8=9`
`x=9+8-18`
`x=-1`
So the solutions are x=-1,y=0,z=6 and w=4
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